What does fuel presure guage read at idle and various RPMS?

trying to determine if I have an issue.

Thanks!

Bill,
Idle - 34 psi
5000 rpm - 28-29 psi
Jamie

Hey Bill last time I was out in my Top Gun the port fuel gauge went to 90+ found a broken wire at the sender in the fuel rail which is right under the air cleaner on the port side of the engine


Drew

I bought the boat used; and from day 1 both engines have read 20-21 lbs from idle to WOT. Since both motors were identical, I assumed that was normal for a TG & 575SCi's.

Well, the diapham fuel pumps have been leaking fuel into the oil of the seawater pump and thus trashing the seals. Merc "JUST" updated the mech fuel pump to a new/revised design mech pump. They have been back ordered until last week. So last week I put on brand new sea water pumps and the new revised mech. fuel pump. At idle I am still getting 20 - 21 lbs. At 4000ish it dropped to about 18 lbs. I didn't take it into boost, as I was unsure of a possible lean condition. (FYI - I still have soot on transom)

I asked the tech to call Merc, and Merc said I should be at about 30 PSI. So now the tech will be looking for a problem. 1st thing he is going to do is hook up a mech fuel pres gauge to rail and see if gauges/senders are wrong. (btw - all wires on senders are good clean connections)
If mech gauge shows low, where would you look for fuel delivery restrictions on an '02 Top Gun???

Thanks in advance!!!!!

Run an independent mechanical gauge on your fuel rail, I think your senders might be off.

Size Matters on the post above has the numbers my friend with 575sci is running also

Mine shows about the same as yours Bill right at 20-25psi.

Bill,
Do you have electric pumps on the bulkhead feeding your mech. pump on the motor? Mine have regulators on them so you can adjust fuel pressure.
Jamie

check the regulators....they get stuck at times and may even obstruct the fuel delivery

I have stock 575SCi's w/ cool fuel.
There is the (new) mech fuel pump that feeds the merc fuel pump which is monted on the motor. If there is an adjustment for this, I don't have a clue.

I didn't trust the gages on the dash so I put pressure gages on the fuel rail. The rail gages read between 28-30 and the dash ones read 5-7 less.

Be careful, these motors don't like low fuel pressure.